A(a) solution is a homogeneous mixture of particles so small they cannot be seen without microscopes and will never settle to the bottom of their container .
Answer: A) Solution
Explanation
A solution contains two components- a solute that exists in solid-state and a solvent that exist in liquid state.
When the solute and solvent are combined in certain conditions( temperature or pressure) a solution is formed.
A solution can be uniform or homogeneous and non-uniform or heterogeneous.
Examples of a uniform homogeneous solution are salt in water and heterogeneous mixture is sand in water.